feat: outputting in GitHub Actions error format (#446)

Author: DeveloperC286

end-to-end-tests/features/github_actions_output.feature

@@ -0,0 +1,13 @@
+Feature: GitHub Actions output format emits workflow commands for linting errors.
+
+
+  Scenario Outline:
+    Given the repository "<repository>" is cloned and checked out at the commit "<checkout_commit>".
+    When linting from the "<commit_hash>".
+    And the argument --output is provided as "github".
+    Then the GitHub Actions output contains a merge commit error.
+
+
+    Examples:
+      | repository                             | checkout_commit                          | commit_hash                              |
+      | https://github.com/asomers/mockall.git | 231bd5ff58ed4f9e99bba74f0239995942f8d29d | e02d8f08f8ab114c79a0e8cf5bd6de860f0f7c2e |

end-to-end-tests/features/steps/assertions.py

@@ -40,3 +40,9 @@ def assert_error_is_one_of(result, errors):
     assert result.stderr in errors, "Expected standard error to equal one of these errors.\n" + \
         f"Standard error = {result.stderr.encode()}.\n" + \
         f"Errors         = {errors}.\n"
+
+
+def assert_output_contains(result, output):
+    assert output in result.stdout, "Expected standard output to contain the output.\n" + \
+        f"Standard output = {result.stdout.encode()}.\n" + \
+        f"Output          = {output.encode()}.\n"

end-to-end-tests/features/steps/then.py

@@ -9,6 +9,7 @@
     assert_error_matches_regex,
     assert_no_errors,
     assert_no_output,
+    assert_output_contains,
 )
 
 
@@ -79,3 +80,12 @@ def assert_ambiguous_shortened_commit_hash_error(context, shortened_commit_hash)
 
     # Then
     assert_error_matches_regex(result, ambiguous_shortened_commit_hash_error)
+
+
+@then('the GitHub Actions output contains a merge commit error.')
+def assert_github_output_contains_merge_commit_error(context):
+    result = execute_clean_git_history(context)
+    assert_command_unsuccessful(result)
+    assert_output_contains(result, "::error title=Merge Commit::")
+    assert_output_contains(result, "::group::")
+    assert_output_contains(result, "::endgroup::")

end-to-end-tests/features/steps/when.py

@@ -9,3 +9,8 @@ def set_linting_from_the(context, git):
 @when('the argument --max-commits is provided as "{max_commits}".')
 def set_max_commits(context, max_commits):
     context.arguments += f" --max-commits {max_commits} "
+
+
+@when('the argument --output is provided as "{output}".')
+def set_output(context, output):
+    context.arguments += f" --output {output} "

src/linting_results/github_actions.rs

@@ -0,0 +1,49 @@
+use std::fmt::Write;
+
+use super::{CommitError, CommitsError, LintingResults};
+
+pub(crate) fn print_all(results: &LintingResults) -> String {
+    let mut output = String::new();
+
+    if let Some(commit_errors) = &results.commit_errors {
+        for commit in &commit_errors.order {
+            if let Some(errors) = commit_errors.errors.get(commit) {
+                let short_hash = &commit.hash[..7.min(commit.hash.len())];
+                let message = commit.message.lines().next().unwrap_or_default();
+
+                let _ = writeln!(output, "::group::{short_hash} - {message}");
+
+                for error in errors {
+                    match error {
+                        CommitError::MergeCommit => {
+                            let _ = writeln!(
+                                output,
+                                "::error title=Merge Commit::Commit {short_hash} is a merge commit."
+                            );
+                        }
+                    }
+                }
+
+                let _ = writeln!(output, "::endgroup::");
+            }
+        }
+    }
+
+    if let Some(commits_errors) = &results.commits_errors {
+        for commits_error in &commits_errors.errors {
+            match commits_error {
+                CommitsError::MaxCommitsExceeded {
+                    max_commits,
+                    actual_commits,
+                } => {
+                    let _ = writeln!(
+                        output,
+                        "::error title=Max Commits Exceeded::Maximum commits exceeded: found {actual_commits} commits, but maximum allowed is {max_commits}."
+                    );
+                }
+            }
+        }
+    }
+
+    output
+}

src/linting_results/mod.rs

@@ -2,19 +2,18 @@ use std::collections::{HashMap, VecDeque};
 
 use crate::commits::commit::Commit;
 
+mod github_actions;
 mod pretty;
 
 /// The representation of an error that an individual commit can have.
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
 pub enum CommitError {
-    /// Commit is a merge commit (has multiple parents).
     MergeCommit,
 }
 
 /// The representation of an error for the collection of commits as a whole.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum CommitsError {
-    /// The number of commits exceeds the maximum allowed.
     MaxCommitsExceeded {
         max_commits: usize,
         actual_commits: usize,
@@ -51,8 +50,11 @@ pub struct LintingResults {
 }
 
 impl LintingResults {
-    /// Get a pretty representation of the linting results as a string, suitable as output for a user.
     pub fn pretty(&self) -> String {
         pretty::print_all(self)
     }
+
+    pub fn github_actions(&self) -> String {
+        github_actions::print_all(self)
+    }
 }

src/main.rs

@@ -33,7 +33,7 @@ pub(crate) struct Arguments {
     #[arg(
         long,
         default_value = "default",
-        help = "Specifies the format for outputting results, acceptable values are quiet, default, and pretty."
+        help = "Specifies the format for outputting results, acceptable values are quiet, default, pretty, and github."
     )]
     pub(crate) output: Output,
 
@@ -79,6 +79,9 @@ fn run(arguments: Arguments) -> Result<i32> {
             Output::Pretty => {
                 println!("{}", linting_results.pretty());
             }
+            Output::GitHub => {
+                println!("{}", linting_results.github_actions());
+            }
         }
 
         // As we don't want an error printed but linting failed so want to exit unsuccessfully.

src/output.rs

@@ -5,4 +5,6 @@ pub enum Output {
     Quiet,
     Default,
     Pretty,
+    #[value(name = "github")]
+    GitHub,
 }